WO2012020344A1 - Chromium oxide refractory material - Google Patents

Abstract

The invention relates to a device selected from among a glass furnace and a channel for dispensing the glass comprising a block and/or a coating made of a sintered material obtained by sintering a particular mixture comprising a chromium oxide content, indicated as "Cr_T", of between 10% and 82%. The die fraction is such that 0.39.(Cr_T)+24 < Cr_M < 0.39.(Cr_T)+52, Cr_M denoting the chromium oxide content by weight of the die fraction in wt % on the basis of the oxides of the die, and the aggregate is such that x_II ≥ 97%, x_III ≥ 70%, and x_IV ≤ x_III - 70%, Cr_G denoting the chromium oxide content by weight of one grain in wt % on the basis of the oxides of said grain. x_II denotes the amount, in wt % on the basis of the aggregate, of grains having the following conditions (II): if 10% ≤ Cr_T ≤ 30%, then Cr_G ≤ 0.018.(Cr_T)² - 0.390.(Cr_T)+58.8; if 30% ≤ Cr_T ≤ 60%, then Cr_G ≤ 1.22.( Cr_T)+26.7; and if 60% < Cr_T ≤ 82%, then Cr_G ≤ 100. X_III denotes the amount, in wt % on the basis of the aggregate, of grains having the following conditions (III): if 10% ≤ Cr_T ≤ 30%, then 0.018.(Cr_T)² - 0.390.(Cr_T)+9.10 ≤ Cr_G ≤ 0.18.(Cr_T)² - 0.390.(Cr_T)+25.10; if 30% < Cr_T ≤ 60%, then 1.17.(Cr_T) - 21.5 ≤ Cr_G ≤ 1.17. (Cr_T) - 5.5; and if 60% < Cr_T ≤ 82%, then 1.17.(Cr_T) - 21.5 ≤ Cr_G ≤ 1.67. (Cr_T) - 35.5. x_IV denotes the amount, in wt % on the basis of the aggregate, of grains having the following conditions (IV): if 10% ≤ Cr_T ≤ 30%, then 0.018.(Cr_T)² - 0.390.(Cr_T)+9.10 > Cr_G; if 30% < Cr_T ≤ 60%, then 1.17.(Cr_T) - 21.5 > Cr_G; and if 60% < Cr_T ≤ 82%, then 1.17.(Cr_T) - 21.5 > Cr_G. The invention can be used for a glass furnace.

Description

 Refractory product based on chromium oxide

Technical area

 The invention relates to an artificial mixture comprising chromium oxide, to a sintered product made from such a particulate mixture and to a process for producing such a sintered refractory product. This refractory product may in particular be used in an environment in which it is in contact with molten glass

State of the art

 Refractory products include fused and cast products and sintered products. Unlike sintered products, molten and cast products usually comprise a very abundant intergranular glassy phase which fills the network of crystallized grains. The problems encountered in their respective applications by the sintered products and the cast and cast products, and the technical solutions adopted to solve them, are therefore generally different. Moreover, because of the important differences between the manufacturing processes, a composition developed to manufacture a melted and cast product is not a priori usable as such to manufacture a sintered product, and reciprocally

The sintered products are obtained by mixing appropriate raw materials and then shaping this mixture raw and cooking the resulting green part at a temperature and for a time sufficient to obtain the sintering of this green part. Sintered products, according to their chemical composition, are intended for a wide variety of industries,

 Refractories containing chromium oxide are conventionally used in applications where they are subjected to extreme chemical aggression, for example in glass furnaces, particularly as furnace tank blocks, or in furnaces in which they are in contact with a slag.

 The use of such refractory products in contact with a slag or with molten glass is for example known from US Pat. No. 6,352,951 (incineration furnaces containing blocks based on alumina and chromium) and US 4,823,359 (glass furnaces). having coatings of alumina and chromium).

 Corrosion by a slag is different from corrosion by a molten glass and a product suitable for being brought into contact with a slag is therefore not necessarily suitable for an application in which it would be brought into contact with molten glass,

however, there is a continuing need to increase the shelf life of these products.

The object of the invention is to satisfy this need. Summary of the invention

 The invention proposes a particulate mixture consisting of a matrix fraction and a granulate respectively constituted by particles having a size of less than or equal to 50 μτη, called "matrix particles" and particles having a size greater than 50 μιη, called " grains ", the matrix fraction representing more than 10% and less than 45% of the mass of the particulate mixture,

said particulate mixture having a chromium oxide content, denoted "Crr", greater than or equal to 10% and less than or equal to 82%, preferably less than or equal to 80%, as a weight percentage on the basis of the oxides of the refractory mixture ,

the matrix fraction being such that

0.39 (Crr) +24 <Cr _M <0.39 (Cr _T ) +52 (I),

 - Cru denoting the mass content of chromium oxide of the matrix fraction, in percentage by mass on the basis of the oxides of the matrix fraction, and

the aggregate being such that n ≥ 97%, χ _Π ι≥ 70%, and xrv x xm - 70%

- Crc denoting the mass content of chromium oxide of a grain, in percentage by mass on the basis of the oxides of this grain,

 xn designating the quantity, in mass percentage on the basis of the granulate, of groins respecting the following condition (Π):

if 10% ≤ Cr _T ≤ 30%. then Cr _G S 0.018 (CTT) ² - 0.390 (Cr _T ) -58.8;

if 30% <Cr _T ≤ 60%, then Cr _G ≤ 1, 22 (Cr _r ) - 26.7; (II)

if 60% <CIY 82%, in particular 60% <CT _t ≤ 80%, then Cr _G <100,

 xm denoting the quantity, in mass percentage on the basis of the granulate, of grains complying with the following condition (III):

 - if 10% ≤ Crr≤ 30%, then

O.Ol S.CCrr sW.CCrTi + fl.l O≤ Cr _Q ≤ 0.018 (Cr _r ) ² -0 ₍ 390. (Cr _r ) -25.10;

if 30% <Cr _r <60%, then 1.17 (Cr _T ) -21, 5 Cr Cr _G 1, 17, (Cr _T ) -5.5; (III)

^• if 60% <Cr _T <82%, in particular 60% <Cr _T ≤ 80%, then l, l 7. (Cr _T ) -21, 5 <Cr _G ≤ l, 67. (Cr _T ) -35 , 5,

 xiv denoting the quantity, in mass percentage on the basis of the aggregate, of grains complying with the following condition (IV):

- If 10% ≤ Cn <30%, then 0.018 (Cr ₁ ) - 0 _s 390 ₁ (Cr _T >-9.10> Cr _G ;

- If 30% <Cr _T ≤ 60%, then 1, 17, (0 ^ -21.5> Cr ₀ ; (IV)

If 60% <Cr _T ≤ 82%, especially 60% <Cr _T <80%, then 1, 17. (Cr _r ) -21, 5> Cr _u , The response traditionally proposed to increase the life of the products arranged in contact with the molten glass is to improve the corrosion resistance. However, the inventors have, in a new way, sought to make the wear of the products more uniform. They have indeed observed that the "holes" on the surface in contact with the molten glass, corresponding to the zones in which the wear is maximum, limit the lifetime of the products, regardless of their composition.

 They found that the conditions imposed on a product made from a particulate mixture according to the invention advantageously lead to a particularly uniform corrosion profile.

A particulate mixture according to the invention may also have one or more of the following optional and preferred characteristics:

0.39 (Crr) -29 <Cr _M <0.39 (Crr) -'- (V);

0.39 (Crr) -32 <Cr _M <0 _s 39. (Crr) +44.5 (VI);

xii is greater than 98%, preferably greater than 99%, preferably substantially 100%;

 xm is greater than 85% and xr is less than 1%, preferably substantially 0%; At least 70% by weight of the grains have, in percentages by weight on the basis of the oxides, a chromium oxide content satisfying the following condition VIT).

- If 10% ≤Cr _T ≤30%, then

O _f 018 Cr _T) ² -0 90. (CTT) -13,10≤CrG 0.01 8 (Cr _T) ² -0 90. (Cr _T) 21 _f 10;

- If 30% <Cr _T <60%, then 1, 17. (ΟΡ _γ ) -17.5 <Cr <0.17 (Cr _T ) -9.5;

If 60% <Cr _T 82%, in particular 60% <Cr _T ≤ 80%, then 1.67 (Cn -) - 51, S ≤ Cr _G ≤ 1.67 (Crr) -39.5:

- At least 70% by weight of the grains have, in percentage by mass on the basis of the oxides, a content of chromium oxide satisfying the following condition (VIII):

- If 10% <Cr ≤ _T ^'30%

then O _r 018 (Cr _r) ² "0.390 (Cn) -rl3,10 Cr _G ≤ 0.018 (Cr ^_T), -0.390 _(T h21 Cr, ^10..;

- If 30% <Cr-r≤ 60%, then, 17, (Cr _T ) - 17, f5 <Cr _G ≤ 1.17 (Cr _T ) -9.5;

- If 60% <Cr _T ≤ 82%, in particular 60% <Cr _T ≤ 80%, then 1.67 (Cr _T ) -47.5 Cr Cr l, 67 (Crr) -39.5;

- In a particular embodiment, the matrix fraction has a content of chromium oxide "Cr _M " respecting the condition (VI) and at least 70% by weight of the grains have a chromium oxide content "C o" respecting the condition (ΥΊ11); In a second particular package, the matrix fraction has a content of chromium oxide "Cr _M " respecting the condition (VT) and at least 99% by weight of the grains have a content of chromium oxide "Cr _c . "Respecting condition (VIII);

 - At least 90%, preferably at least 95%, preferably at least 99%, preferably substantially 100% by weight of the grains have a content of chromium oxide <Cro "complying with the condition (ΠΙ) and / or the condition (VU);

 The grains and / or matrix particles containing chromium oxide are preferably fi nished particles;

The particles of the granulate and / or the matrix fraction are sintered particles.

The invention also a process for producing a sintered refractory product, comprising the following successive steps:

 A) preparing a feedstock by mixing a particulate mixture according to the invention and water;

 B) shaping said feedstock so as to form a preform; C) sintering said preform.

 The invention also relates to a sintered product obtained by sintering a particulate mixture according to the invention, in particular according to steps A) to C) below.

Preferably, this product has a density greater than 3.1 g / m ^3, or even greater than 3.3 g / m ³ and / or less than 4.5 g / cm ³ or even less than 3 g / cm ⁱ .

The invention finally relates to a device selected from a glass furnace, a regenerator, and a glass distribution channel, also called "feeder channel", comprising a block and or a coating of a sintered product according to the invention,

Definitions

The "matrix tensile" consists of particle size less than or equal to 50 μπι, say "matrix particles"_'These particles are intended to constitute the matrix of the product refractory, the complementary fraction, comprising caused particles having a size greater 50 μνη. or "grains" is called "granulate",

 By "particle size" is meant the dimension of a particle conventionally given by a particle size distribution characterization performed with a laser granulometer. The laser particle size analyzer used for the examples is a LA-95 ™ ca-part of the company HORIBA.

The term "circularity" of an observed particle, the ratio P_y ^' P, P _R designating the perimeter of the particle as observed, and PD designating the perimeter of the disc having the same surface as that of the particle such as observed. Circularity depends on the direction of observation, As shown in FIG. 1b, to evaluate the circularity "Ci" of a particle P, the perimeter of the disk D having an area equal to the area A _p of the particle P is determined on a photograph of this particle. The perimeter P _r of this particle is also determined,

Circularity is equal to the ratio of Pf 'P _r , Thus. iu, _s the particle is of shape

The SYSMEX FPIA 3000 user manual also describes this procedure (see "detail ed specification sheets" on www.malvem.co.uk).

The percentiles or "percentiles" (Ci 1) and 50 (Ci "c) of a set of particles are the circularities of particles corresponding to the percentages, by number, of 10% and 50%, respectively, on the circularity distribution curve. cumulated particles of this set, the circularities of particles being ranked in ascending order. For example, 10% by weight of the particles of this set have a circularity less than Ci 10. Pears can be evaluated using a device of the type of morphology G3 marketed by the company alvern. Cis is still called "median circularity".

 By extension, these pores are used to characterize the distribution of the circularities of the particles of a triturated material obtained from this powder.

 To determine the parents Cijrj and Cijc the set of particles is poured on a flat plate and observed petpendiculai deny this plate. The number of particles counted is greater than 250, which makes it possible to obtain substantially identical pereventiles, regardless of the way in which the particles have been poured onto the plate. A method of detection is described in more detail in the examples herein. -Dessous,

The term "convexity" of an observed particle, the ratio P _c / P _r , P _c denoting the convex perimeter of the particle as observed and P _r denoting the perimeter of said particle as observed, as shown in FIG. figure the. The convexity of a particle depends on the direction of observation.

The percentiles or "percentiles" (Coio) and 50 (COJD) of a set of particles are the particle convexities corresponding to the percentages, by number, of 10% and 50%, respectively, on the cumulative convexity distribution curve. particles of this set, the convexities of particles being ranked in ascending order, for example, 10% by mass of the particles of this set have a convexity lower than Coic. Pears can be evaluated using a Morphologi® G3 type device marketed by the company Malvern. OCOG is still called "median convexity".

By extension, these pins are used to characterize the distribution of the convexities of the particles of a sintered material obtained from this powder, To determine the percentiles C10 and C0511 the set of particles is poured onto a flat plate and observed perpendicularly to this plate. The number of particles is greater than 250, which makes it possible to obtain substantially identical percentiles, regardless of the extent to which the particles have been poured onto the plate. A determination method is described in more detail in the examples below.

 A "granule" is a particle having a circularity greater than 0.85,

The term "particle agglomerated" or "agglomeration" means a particle formed by a set ^of other particles. Agglomerated particles may in particular be obtained by sintering or by means of a binder,

Unless otherwise indicated, all percentages are mass percentages.

 The chemical analyzes or the chemical compositions of the particles refer to the composition of each of said particles. Chemical analyzes or chemical compositions of a "particulate mixture" or "powder" refer to the average composition, on all the particles concerned. Unless otherwise indicated, these compositions are based on oxides.

 Of course. Cro is always less than or equal to 100%, even when one of the relationships above leads to an upper limit that exceeds 100%,

Brief description of the figures

 Other features and advantages of the invention will become apparent upon reading the detailed description and examining the drawing in which

 Figures 1 and 1b illustrate the method implemented to measure convexity and circularity, respectively;

 Figure 2 shows a. a section of a refractory product according to the invention.

detailed description

Particulate mixture

 The manufacture of a particulate mixture according to the invention may result from a mixture of raw material powders having suitable compositions and particle size distributions.

Preferably, the particulate mixture has a C ^O _? Content _. - AljOj greater than 60%, preferably greater than 65%, preferably greater than 70%, preferably greater than 80%, or even greater than 90%, or even greater than 92%, or even greater than 94%, in percentage by weight on the base of the oxides. In one embodiment, the particulate mixture has a chromium oxide content greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 35%, greater than 40½, and / or less than 75%, less than 70%, or less than 65%, less than 50%. In one embodiment, the content of chromium oxide is greater than 50%, or even greater than 55%,

 In one embodiment, the particulate mixture has an Al2O3 content greater than 3%, greater than 5%, greater than 10%, greater than 15%, greater than 20%, greater than 25% and less than 85%, less than 80%, less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, or even less than 35%. In one embodiment, the particulate mixture has an Al2O3 content greater than 35%, greater than 40%, and even greater than 45%,

 The silica content of the particulate mixture may be greater than 0.1%, greater than 0.5%, greater than 0.7%, greater than 1%, and less than 8%, less than 5%, less than 4%. %, less than 3%, less than 2%, or even less than 1, 5%.

The zirconia content of the particulate mixture may be less than 10%, less than 5%, less than 1%, less than 0.5%, or less than 0.1%.

 ΙΛ titanium oxide content of the particulate mixture may be greater than 0.3%, greater than 0.5%, greater than 1%, and / or less than 4%. less than 3%, less than 2%, less than 1, 5%, or less than 1, 3%. In one embodiment, the titanium oxide content of the particulate mixture is less than 0.2%.

Preferably, the total content of Cr 2 O 3, Al 2 O 3, Al 2 O 5, SiO 2 and O 2 _s in the particulate mixture is greater than 90%, greater than 92%, greater than 94%, greater than 96%, greater than 98%. . ΙΛ particle size distribution is not limiting. It can in particular be adapted to the apparent density of the sintered refractory product that it is desired to obtain,

In one embodiment, the ratio Cr 1 Cva is greater than 1.05, greater than 1.1, greater than 1.15, greater than 1, 2, greater than 1.3, greater than 1.4, greater than 1, 5, greater than 1, 6, and less than 7, less than 6.5, less than 6.0, less than 5.5, less than 5, or less than 4.5 or less than 4.0, lower at 3.5, less than 3.0, less than 2.5, less than 2, less than 1.7. In one embodiment, the Cr 'Cr ratio is less than 0.95, less than 0.9, less than 0.85, less than 0.8, less than 0.75, less than 0.7, less than 0.65, less than 0.6, less than 0.55,

Matrix fraction

A particulate mixture according to the invention preferably comprises more than 15%, more than 20%, more than 25%, and less than 40% or even less than 35% or even less than 30% of matrix particles, in weight percent based on the particulate mixture. Preferably, the matrix fraction and preferably at least 80% by weight of the matrix particles have a chemical composition such that, in mass percentages on the basis of the oxides and for a total of 100%:

Cr ₂ O ₃ - Al ₂ Oj - ZrO ₂ - MgO - Fe 2 O τ Si0 ₂ - Ti0 ₂ ~ CaO≥ 90%, preferably Cr ₂ ¼ - Al ₂ O ₃ - ZrO ₂ - MgO - F¾O ₃ - SiO ₂ - TiO ₂ + CaO 95%, and

Cr ₂ O ₃ - Al ₂ O ₃ - MgO≥ 50%, and

Cr ₂ 0 ₃ ≥ 7%, and

15%> Si0 ₂ ≥ 0.1%, and

 other oxides: <10%, preferably <5%,

Preferably, at least 90% by weight of the matrix particles have a size of less than 40 μιη, preferably it is less than 30 μιη, preferably less than 20 μπι, or even a mféricure at Ι Ο ιη.

 Preferably, the composition of the matrix fraction is such that

the total content Cr ₂ O ₃ - Al ₂ O ₃ + MgO is greater than 65%, preferably greater than 70%, preferably greater than 80%, or even greater than 90%, as a weight percentage on the basis of the oxides; /or

the content of SiO ₂ is less than 12%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, or even less than 4%, or even less than 3; % and or

the TiO ₂ content is less than 7%, even less than 4%, or even less than 3%, or even less than 2%; and or

 the content of "other oxides" is less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1%.

In some embodiments, the matrix tensile composition is such that Cr ₂ O ₃ Al ₂ O ₃ > 80%, Cr ₂ O ₃ - Al ₂ 0 ₃ > 90%, or even Cr ₃ --Al ₂ O ₃ > 95%

In certain embodiments, the composition of the matrix fraction is such that the TiO ₂ content is less than 0.2%,

In certain embodiments, the composition of the matrix fraction is such that the Al ₂ O _{3 content} is greater than 5%, greater than 7.5%, greater than 10%, greater than 15% and / or less than 72%, less than 65%, less than 60%, less than 50%,

Preferably, the matrix particles contain a Cr ₂ 0 -Al ₂ O ₃ solid solution and / or a Cr ₂ 0 -MgO spinel, for example MgCr ₂ O 4, and / or Cr ₂ O ₃ spinel spinel. iron oxide, for example FeCr ₂ · 04, and / or AljOs-MgO-based spinel, for example Al ₂ O ₄ , and / or a Fe-O-oxidic iron spinetle, for example FeA 2, and / or at least one of their solid solutions.

 More preferably, the sum of the oxide contents in the particles of the matrix fraction represents more than 90%, more than 95%, or even substantially 100% of the mass of said matrix particles.

The matrix fraction is preferably composed of chromium oxide particles on the one hand and particles of alumina and / or particles of zirconia and / or particles of magnesia and / or particles of aluminum oxide on the other hand. iron oxide and / or titanium oxide particles and / or silica and / ^'or calcium oxide particles, preferably, the matrix fraction consists of particles composed of chromium oxide on the one hand and, on the other hand, alumina and / or zirconia and / or magnesia and / or iron oxide and / or titanium oxide and / or silica and / or calcium oxide, or mixtures of such particles. For example, the matrix fraction may be a mixture of chromium oxide particles and alumina particles, but may also consist of chromium oxide and alumina particles, in the form of, for example, a solid solution. Preferably, the matrix particles are composed of chromium oxide on the one hand and. on the other hand, alumina and / or calcium oxide and / or zirconia and / or titanium oxide,

 The amount of zirconia matrix particles is preferably less than 10%, preferably less than 8%, preferably less than 5%, preferably less than 3%, by mass percentage based on the oxides of the particulate mixture.

 The median size of the matrix particles may be less than 25 microns, less than 15 microns, less than 10 microns, or even less than 7 microns,

 In one embodiment, the particulate mixture does not contain zirconia particles, especially zirconia matrix particles.

aggregate

^The n particulate mixture according to the invention comprises preferably less than 85% or even less than 80% or even less than 75% of grains, by percentage weight based on the particulate mixture.

The granulate preferably consists of chromium oxide particles on the one hand and particles of alumina and ^/ or particles of zirconia and ^/ or particles of magnesia and ^/ or particles of aluminum on the other hand. iron oxide and / or titanium oxide particles and silica particles. The granulate preferably consists of particles composed of chromium oxide on the one hand and, on the other hand, alumina and ^/ or zirconia and ^/ or magnesia and / or iron oxide and / or of titanium oxide and / or silica, or mixtures of such particles. For example, ic granulate can be a mixture of particles of chromium oxide and alumina particles, but also be a mixture of chromium oxide particles and alumina, in the form for example of a solid solution. Preferably, the grains are composed of chromium oxide on the one hand and, on the other hand, of alumina and or of zirconia and or of titanium oxide.

Also preferably, the particulate mixture does not contain zirconia particles of size between 50 μηα and 500 μιη, preferably does not contain zirconia particles in the granulate. Advantageously, the stone release resistance of the refractory product obtained from the refractory mixture in contact with molten glass is improved,

The standard deviation of the distribution of the chromium oxide content of the grains is preferably less than 8, preferably less than 4, preferably less than 1, 5, preferably less than 1, more preferably less than 0, 75. The difference between the contents of chromium oxide 11a weak and strong is preferably less than 9%, preferably less than 6%, preferably less than 4.5%, All grains then have levels of similar chrome,

More preferably, whatever the constituent considered, provided that its content is greater than 1% by mass percentage on the oxide basis, the standard deviation of the distribution of its content between the different grains is less than 8, preferably less than at 4, preferably less than 1, 5, preferably less than 1, more preferably less than 0.75, all the grains then have similar compositions.

Preferably, the aggregate has a bulk density greater than 85% theoretical density, ^'preferably greater than 88%. preferably greater than 90%, preferably greater than 91%, preferably greater than 92% of the theoretical density, even greater than 93%, or even greater than 94%, or even greater than 95%, or even greater than 96% of the theoretical density,

Preferably, the granulate has an open porosity of less than 10%, preferably less than 6%, preferably less than 5%, preferably less than 3%, preferably less than 2%, preferably less than 1%, or even less than 0.7%, or even less than 0.6%.

 The granulate. may contain granules, that is to say substantially spherical particles. Preferably, the granulate has a median circularity greater than 0.87. Preferably, the granules are agglomerated particles, especially retted particles.

In a particular embodiment, at least 80%, preferably at least 90%, preferably at least 95%, preferably at least 99%, or even substantially 100% by number of grains are granules, Preferably, the granulate and preferably at least 80% by weight of the grains, preferably granules of the granulate, have a chemical composition such that, in mass percentages on the basis of the oxides and for a total of 100%:

Cr ₂ 0 ₃ - Al2O3 - Zr0 ₂ - GB - F¾0_ - Si0 ₂ - Ti (¼ ≥ 90%, preferably Cr ₂ 0 ₃ + Al2O3 ^{■ '■} Zr, ^■ · ^■ MgO - Fな0 ₃ - SiC¾ - Ti0 ₂ ≥ 95%, and

Cr ₂ O ₃ - Al ₂ O ₃ , MgO> 60%, and

 C1-.O3≥9%, and

20% ≥SiO ₂ ≥0.5%, and

 other oxides: ≤ 10%, preferably ≤ 5%,

Preferably, at least 90% by weight of the grains, preferably granules, have a size greater than 100 μ ^η α, preferably greater than 200 μτη, preferably greater than 300 μπι, preferably greater than 400 μηι,

 The inventors have discovered that, remarkably, a refractory product based on chromium oxide using such granules has good thermal shock resistance and high corrosion resistance.

 Preferably, the composition of the granulate is such that

- the total content of Cr ₂ Oj - Al ₂ Oj ^■ - ^■ MgO is greater than 65%, preferably greater than 70%, preferably greater than 80%, or even greater than 90%, or even greater than 92%, or even greater than 94%, as a weight percentage based on the oxides; and / or the SiO 2 leneur is less than 16%, preferably less than 13%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, or even lower. at 4%, or even less than 3% (advantageously, the densification is improved, without the corrosion resistance being reduced); and or

the TiO ₂ content is greater than 0.5%, or even greater than 0.7%, and / or less than 4%, preferably less than 3%, less than 2.2%, or even less than 2%; and or the content of "other oxides" is less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1%.

In some embodiments, the composition of the granulate is such that Cr ₂ O ₃ - Al ₂ O ₃ > 80%, Cr ₂ O ₃ - Al ₂ O ₃ > 90%, or even Cr ₂ O ₃ - Al ₂ O ₃ > 95%.

 In a first particular embodiment, the composition of the granulate, preferably granules of the granulate, is such that, in mass percentage on the basis of the oxides.

Cr ₂ Oj: 9% to 50%: * A1 ₂ 0 ₃ : 45% to 88%;

SiO ₂ <20%, preferably SiO ₂ <16%, preferably SiO ₂ <13%, preferably SiO ₂ <10%, preferably SiO ₂ <8%, preferably SiO ₂ <6%, preferably Si <3 <5%, preferably SiO ₂ <4%, preferably SiO ₂ <3%;

^■ Fe20 ₃ <1%;

^■ gO <0.5%;

* 0.5% <Ti (な <4%, or even Ti0 ₂ <2%;

Zr0 ₂ <5%;

 - other oxides <2%, preferably: other oxides <1%.

The Cr ₂ 0 _{3 content} can be between 10% and 20%, between 20% and 30%, between 30% and 40%, or between 40% and 50%, and the content of A1 ₂ 0 ₃ can be included. between 45% and 55%, between 55% and 65%, between 65% and 75%, or between 75% and 88%.

 In a second particular embodiment, the composition of the granulate, preferably granules of the granulate, is such that, in mass percentage on the basis of the oxides:

Cr ₂ O ₃ : 50% to 95%;

 - AI2O3: 2% to 45%;

- Si0 ₂ <20%, preferably Si0 ₂ <16%, more ^'preferably Si0 ₂ <13%, preferably SiO ₂ <10%, preferably Si0 ₂ <8%, preferably Si0 ₂ <6%, preferably Si0 ₂ <5%, preferably Si0 ₂ <4%, preferably Si0 ₂ <3%;

Fe ₂ O ₃ <1%;

 - MgO <0.5%;

- 0.5% <Ti0 ₂ <4%, or even Ti0 ₂ <2%;

 Zr <¼ <5%;

 - other oxides <2%, preferably; other oxides <1%.

 The content may be between 50% and 60%, between 60% and 70%, between 70% and

S0 な, or between 80% and 95%, and where the Al2O3 content may be between 2% and 12%, between 12% and 22%, between 22% and 32%, or between 32% and 45%,

 In a third particular embodiment, the composition of the granulate, preferably granules of the granulate, is such that, in mass percentage on the basis of the oxides:

Cr ₂ O ₃ : 95% to 99%;

- A1 ₂ 0 ₃ : 0 to 4%;

- If <¼ <4%, preferably Si0 ₂ <3%, preferably Si0 ₂ <2%, preferably SiO2 <1%;

- Ft¾0 ₃ <4%; gO <0.5%;

- 0.5% <TiOj <5%. even Ti0 ₂ <4%, even T1O2 <2%;

Zr0 ₂ <4%;

 - other oxides <2%, preferably: other oxides <1%.

In a fourth particular embodiment, the composition of the granulate, preferably granules of the granulate, is such that, in mass percentage on the basis of the oxides:

• Cr _a 0 ₃ : 15% to 50%;

- A1 ₂ 0 ₃ : 10% to 80%;

- 1% <F02O3 <30%, or even 3% <Fe ₂ 0 ₃ ;

 - 0.5% <MgO <20%, preferably MgO <10%;

SiO ₂ <20%, preferably SiO ₂ <16%, preferably SiO ₂ <13%, preferably SiO ₂ <10%, preferably SiO ₂ <8%, preferably SiO ₂ <6%, preferably SiO ₂ < 5%, preferably SiO: <4%, preferably SiO ₂ <3%;

• 0.5% <T <0 ₂ <4%, even T1O2 <2%;

■ Zr0 ₂ <5%;

 • other oxides <2%, preferably: other oxides <1%.

The Cr ₂ O ₃ content may be between 15% and 25%, between 25% and 35%, or between 35% and 50%, and / or the content of Alj.Qj may be between 10% and 20%, between 20% and 30%, between 30% and 40%, between 40% and 50%, between 50% and 60%, between 60% and 70%, or between 70% and 80%, and-or the F content. jO. _? can be between 3% and 10%, between 10% and 20%, or between 20% and 30%.

Preferably, the grains, preferably granulate granules contain a solid solution CrjOj-A-Hoj and or spinel based on Cr ₂ O MgO, e.g. MGCR ₂ 0;., And / or a spinel based on Cr ₂ 0 ₃ -oxide of iron, for example fccr ₂ U4, and / or a spinel-based a-Oj MgO, e.g. MgAljO * and / or spinel based A1.0 ₃ iron -oxide , for example FeAljO-i, and / or at least one of their solid solutions,

 Preferably still, the sum of the oxide contents in the grains, preferably the granules of the aggregate, represents more than 90%, more than 95%, or even substantially 100% of the mass of said grains or granules.

In one embodiment, the granulate and the matrix fraction have substantially identical compositions. In one embodiment, these compositions are different. In one embodiment, the granulate is made up of sintered particles for more than 90% of its mass. Preferably, the granules of the granulate are sintered particles.

Preferably, the granulate present - a bulk density greater than 3.0 g ^{'cm _3;} preferably greater than 3.3 / cm *, or even greater than 3.5 g / ^{'cm 3,} or even greater than 3.6 g'cm ^3; and or

 > an apparent density greater than 85% of the theoretical density, preferably greater than 88%, preferably greater than 90%, preferably greater than 91%, preferably greater than 92% of the theoretical density, or even greater than 93%; or even greater than 94%, or even greater than 95%, or even greater than 96% of the theoretical density (advantageously, the flowability of the particulate mixture is improved); and or

 an open porosity less than 10%, preferably less than 6%, preferably less than 5%, preferably less than 3%, preferably less than 2%, preferably less than 1%, or even less than 0.7%; %, or even less than 0.6%. The corrosion resistance of the refractory product obtained from the refractory mixture, in particular by contact with molten glass, is improved.

More preferably, more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 99% by weight of the granules, or even grains, of the granulate, preferably substantially all the granules of the granulate, even substantially all the grains of the granulate have a size greater than 200 μιτι, preferably greater than 300 μτα, preferably greater than 400 μν, or even greater than 0.5 mm and / or less than 10 mm, preferably less than 5 mm .

Still preferably, the particulate mixture contains at least 10% of grains larger than 2 mm in weight percent.

Preferably, the granulate has:

 a median circularity greater than 0.88, preferably greater than 0.90, preferably greater than 0.1, preferably greater than 0.92, preferably greater than 0.93; (advantageously, the resistance to thermal shocks is improved); and or

a circularity Ci 10 greater than 0.72, preferably greater than 0.74, preferably greater than 0.76, preferably greater than 0.78, preferably greater than 0.80, preferably greater than 0.82; and or

 a median convexity COJO greater than 0.90, preferably greater than 0.92, preferably greater than 0.94, preferably greater than 0.95, preferably greater than 0.96; "/or

a convexity Co: o greater than 0.80, preferably greater than 0.82, preferably greater than 0.85. preferably greater than 0.88, preferably greater than 0.90; and or - a circulai! the median greater than 0.90, preferably greater than 0.92, and an open porosity of less than 2%, preferably less than 1%,

Preferably, the characteristics relating to the chemical composition of a granulate as defined above, and in particular the optional characteristics above, are applicable to more than 80%, more than 90%. or more than 95% or more than 99% by weight, or substantially 100% o aggregate grains.

 Additive

 The porticidal mixture may also contain at least 0.1% by weight of a shaping additive.

The additive may in particular be chosen from the group consisting of:

■ clays;

 plasticizers, such as polyethylene glycol (or "FEG") or polyvinyl alcohol (or "PVA");

 cements, preferably with a high alumina content;

■ hydratable aluminas, such as bociimite;

^"Binders which organic temporary binders such as resins, lignosulphonates, the carhox \ méthyiceliulosc or dextrin;

 deflocculants, such as polyphosphates of alkali metals, polyacrylates of alkali metals, polycarboxylates; and

- mixtures of these products.

 Preferably, the shaping additive is selected from the group consisting of cements, deflocculants, clays, lignosulfonates, PVA and mixtures thereof.

 Preferably, the content of the shaping additive is less than 6%, in weight percent on the basis of the particulate mixture. Preparation of a particulate mixture according to the invention

 Sintered particles, and in particular a granulate of sintered particles, can be manufactured according to a conventional method comprising the following successive steps:

 a) preparation of a feedstock by mixing raw materials and water;

 b) shaping said feedstock so as to form a set of particles;

 c) frigest particles obtained in step b).

An exemplary method is described in detail in the examples, In step a), the mixture of the raw materials is adapted so as to obtain particles having the desired chemical composition. Any mixing means may be used, for example an intensive mixer or kneader.

 In step b), preferably, the shaping does not involve atomization operation. An id process leads indeed to a low density. An atomization operation also leads to particles having a small size, which makes the manufacture of spherical grains difficult. Step b) may comprise a granulation operation. Such an operation can not, however, guarantee obtaining a median circularity greater than 0.8? and a density greater than 85% of the theoretical density. To obtain such a result, an intensive type mixer is preferably used, preferably with a vortex end speed greater than 6 m sec, and with a sequential feed of said feedstock mixer,

In step c), the particles are sintered, for example in a baking oven. All baking ovens can be used, such as, for example, intermittent ovens, but also rotary ovens. The parameters of the sintering are determined according to the composition of the particles,

The sintering temperature may be between 1400 ° C and 1700 ⁵ C, The sintering may be carried out in air, but also in a neutral condition (under nitrogen for example), even under reducing conditions (in excess of carbon monoxide e.g. ). Preferably, the sintering is carried out under air.

The dwell time can be between i. hour and 10 hours, preferably between 2 hours and 5 hours.

 The open porosity can be adjusted by changing the particle size distribution of the particulate raw materials used, or by acting on the temperature and / or the bearing time during sintering.

Method of manufacturing a refractory product

 A refractory mixture according to the invention can be advantageously used to produce products having a granulate bound by a binder matrix,

For this purpose, a method comprising steps A) to C) described above can be implemented. This process advantageously makes it possible to manufacture a sintered refractory product having a bulk density of between 3.1 and 4.5 g cm -1, preferably between 3.3 and 4.3 g / cm ^3. The Andreasasen compaction models or Fuller-Bolomey can be used to change the apparent density of sintered refractory products. Such compaction models are particularly described in the book entitled "Treaty of ceramics and mineral materials", CA, Jouenne, Septima Editions, Paris (1984), pages 403 to 405.

 In step A), matrix particles and grains are mixed, preferably with a shaping additive, to form the feedstock.

Preferably, the grains comprise granules as described above, preferably thermally consolidated, preferably sintered. The granules can thus advantageously retain their spherical form during their handling,

 The particulate mixture can also be delivered ready-to-use. It is then sufficient to mix it with water to prepare the starting charge,

The amount of water is a function of the process used in step B).

 In the case of forming by cold pressing, an addition of a quantity of water of between 1.5% and 4¼, in weight percentage based on the particulate mixture without the additives, is preferred. Shaping involving a hydraulic connection, such as pouring, addition of a quantity of water of between 3 and 7%, by mass percentage on the basis of the particulate mixture without the additives, is preferred.

 Without being able to explain it theoretically, the inventors have discovered that the substantially spherical shape of the granules improves resistance to thermal shock, regardless of the open porosity of the granulate,

 The inventors have also discovered that the open porosity of the granulate influences the flowability of the feedstock. In fact, if the substitution of chamotte grains by a granulate having an open porosity greater than 10% leads to a degradation of the flowability, Unexplained way, when the open porosity of the granulate used is less than 6%, the flowability is higher than that of conventional products with chamotte grains. Flowability is further improved when the open porosity is less than 2%.

In step C), the sintering conditions, and in particular the sintering temperature. depend on the composition of the particulate mixture. Typically, a sintering temperature between 1400X and 170 ° C, preferably between 1500 C ⁵ and 1600 ° C is well suited, At the end of step C), there is obtained a sintered refractory product according to f the invention,

Such a product is shown in FIG. 2. In particular, the substantially circular particles 10 according to the invention and the matrix 12 are clearly distinguished.

 The sintered refractory product may have a bulk density greater than 3.00, greater than 3.10, greater than 3.30, greater than 3.50, and / or less than 4.30, or greater than 4.20.

It may have an open porosity greater than 10%, greater than 12%, greater than 1%, and / or less than 20%, less than 18%, or even less than 15%. The properties of this product make it particularly well suited for use in a glass furnace, a regenerator, or a feeder channel.

 A sintered product according to the invention can be used in the form of a block or a layer, for example in the form of an applied lining, by any known method, on a wall to be protected. The sintering can be carried out in situ, that is to say after the product has been placed in its service position.

Examples

 To manufacture the grains "chromium oxide, alumina, silica, titania" used in the products of Examples 2, 3, 4, 6, 7, 8 and 9 mentioned below, the following raw materials were used:

^■ chromium oxide Cr: 0 ₃ pigment with a purity higher than 95%, with a specific surface area equal to 4m ² / g and a median Lailk of 0.7 μπι;

■ · alumina Al: Os greater than 99% purity, having a specific surface of 7 m ^s / g, and a median size of 0,6μιη;

 - silica fume with a purity higher than 92%;

 • titanium oxide, in the rutile form, with a purity greater than 93% and having a median size of 1.5 μηι.

 These raw materials were dosed and mixed in order to present the desired chemical composition.

 For each example, 3000 g of oxide mixture, 350 g of water and 150 g of polyvinyl alcohol (PVA) are introduced into an Eirich RV02 mixer,

 The assembly is then kneaded for 1 minute, with a vortex rotating at 300 rpm and a tank set at 43 rpm in order to obtain a homogeneous mixture. The rotational speed of the vortex is then increased to 1 50 rpm, and an additional 900 grams of the oxide mixture is then gradually added in one minute, the rotation is maintained 2 minutes after the end of Γ introduction of the additional amount of charge, the particles are then discharged, dried under air 24h at 110 ° C. before being stirred at 1550 ° C. for a dwell time of 3 hours, under air, with a temperature rise rate and a temperature descent rate of SOT-h. After sintering, the particles are sieved and the particle size range 0.5 - 5 mm is retained.

M grains "chromium oxide, alumina, silica, titanium oxide" used in the product of Example 10 were manufactured by extrusion of the same mixture as that used in the manufacture of the grains used in the product of Example 9 , in order to obtain breads extruded. These extrudates loaves were then sintered in air in a heat cycle having a bearing 3 hours at 1550 ^C C, and finally ground and screened to obtain the size fraction from 0.5 to 5 mm.

 Refractory products were then manufactured according to steps A) to C) above. In step A), the feedstock was prepared by mixing a quantity of water of between 4.1% and 4.7% with a particulate mixture adapted to the desired chemical composition, The following raw materials were used:

"AZS" grains of the ER-1681 electro-cast refractory product manufactured and marketed by the European Company of Refractory Products, and containing as a percentage by mass on the basis of the oxides; 32.5% Zr0 _2, 51% Al ₂ 0 _3, 1 5% of SiO and _has 1, 3% Na ₂ 0 (used in the product of Example 1), maximum size below 5 mm;

"AZS-Cr" grains of ER-2161 electrotubunic refractory product manufactured by the European Company of Refractory Products, and containing as a percentage by mass on the basis of oxides: 27% Cr ₂ 0 ₃ , 27% Zr0 ₂₎ 28% Al ₂ 0 ₃ , 14.5% SiO ₂ and 1.1% Na ₂ O (used in the product of Example 5), maximum size less than 5 mm;

"High chromium" grains containing 92% Cr ₂ O ₃ and having an open porosity of less than 3% (used in the product of Example 1 *), with a maximum size of less than 5 mm;

"High chromium" grains containing 98% Cr ₂ 0 ₃ and having an open porosity of less than 3% (used in the product of Example 5 *), with a maximum size of less than 5 mm;

- Grains "chromium oxide, alumina, silica, titanium oxide", with a maximum size of less than 5 mm, exhibiting, depending on the products of the examples considered, the characteristics appearing in the following Table 1;

De l'oxyde de chrome CrjOî pigmentaire d'une pureté supérieure à 95°/., présentant une surface spécifique égale à 4 m^!/g et une taille médiane de 0,7 μηι ;

Crystalline chromium oxide with a purity greater than 95% having a specific surface area of 4 m ^. / g and a median size of 0.7 μηι;

Alumina Al2O2 with a purity of greater than 99%, having a specific surface area equal to 7 mVg, and a median size of ϋ, 6μιη;

- Zirconia with a purity higher than 98.5% having a median size of 3μιη. ;

 Titanium oxide, in the rutile form, with a purity higher than 93% and having a median size of 1.5 μιη.

3% of a shaping additive (alumina cement CA25 marketed by ALMATYS) were added to the feedstock.

In step B), the initial charge was shaped by a vibrocolding technique in the form of a preform with dimensions adapted to the measurement to be made.

 In step C), the preform obtained was then dried and sintered under air at a temperature of

1 S50 ^S C, for 10 hours.

 The following measures have been carried out:

The measurement of the open porosity of a set of particles was carried out according to the following method;

Dry at 110 ° C for at least 12 hours, 4 samples of 35 grams each consisting of particles whose size is between 2 and 5 mm. The dry mass of each of the samples is noted Psi, Ps _2> P-3 and PS4. We dump Ps = Ps-Ps: -Ps3- ^i- Ps4.

- Place each sample in a vial,

 - Using a vacuum pump, vacuum at least 0.07 MPa in each vial and maintain this vacuum for 7 minutes. Then introduce water into the flask to cover the particles with at least 2 cm of water, which allows the particles to always be covered with water during subsequent evacuation.

- Make a vacuum of 0.08 MPa in each flask containing the particles and water, and maintain this vacuum for 7 minutes, break the vacuum,

 - Make a vacuum of 0.08 MPa in each bottle, and maintain this vacuum for 7 minutes.

 Break the void,

 Make a vacuum of 0.08 MPa in each bottle, and maintain this vacuum for 7 minutes. Break the void.

 - Determine the submerged weight of each sample, Pi ;, 12, P13 and P14. We denote Pi = Fii-Pi2-Pi3-P4.

Pour the contents of the 4 bottles on a 2 mm square mesh sieve to remove the water. Then pour the particles on a dry cotton cloth to eliminate excess water and wipe off the particles until the moisture luster has disappeared from their surface,

 - Determine the wet weight Ph of all the particles,

The open porosity of the set of particles is equal to (Ph-Ps) / (Ph-Pi).

These measurements are always performed on sets of sintered particles. They correspond to average measurements on the material constituting the particles, that is to say do not take into account the interstices between the different particles.

 The measurements of the apparent density and of the open porosity of a sintered product were carried out on samples of dimensions 125 × 25 × 25 mm -1 according to the ISO 501 7 standard. The Ciso and Ciio circularities and the C.sub.w convexities. and Wedge of a set of particles can be evaluated by the following method:

A sample of particles having sizes between 0.5 and 2 mm is poured onto the glass plate provided for this purpose a device orphologi ⁸ G3 marketed by the company Malvern. The magnification selected is IJC. The analysis is launched. In order to avoid the recognition of any scratches of the glass plate and dust, the measurements corresponding to particles having a width ("width") of less than 0.4 mm are eliminated from the count by creating a filter (" width <400 "), the number of particles counted after filtering is greater than 250.

 The apparatus provides an evaluation of the circularity distribution ("Circularity") and convexity ("Convcxity"), the particles being counted in number.

 It is also possible to estimate the distribution of the circularities and convexities of the particles present in a sintered product by a cliché analysis of a section of said product, as represented in FIG. 2.

 The chemical analyzes were carried out by X-ray fluorescence with respect to the constituents whose content is greater than 0.5%. The content of the constituents present at a content of less than 0.5% was determined by AES-ICP ("Atomic Spectoscopy-Inductively Transmitted (Plasma).

To measure the average corrosion rate and the roughness index, samples in the form of cylindrical bars having an initial radius r _c . equal to 1 1 mm and 100 mm in height were taken and subjected to a test of rotating the immersed samples in a bath of molten glass, brought to a temperature T determined according to the composition of said glass, the speed sample rotation was 6 rpm. The samples were kept immersed for a period of time "t", at the end of this period and after cooling, the part of a sample which has been immersed in the glass (of height K equal to 30 mm) has a section in the form of an ellipse of small axis Pa and of long axis Ga, for each sample is determined the minimum value of Pa (Pam) in mm, the maximum value of Pa (PaM) in mm, the mkumalc value of Ga (Gain) in mm and the maximum value of Ga (GaM) in mm. We set Pa ^ y ^ = (Pam-PaM) 2 and Ga ™ _yCT = (Gam ~ GaM) / 2. For each sample, the average remaining volume Vr _nuyK i is determined by the formula Vr _av - _B "(, l-ia Pamoye, GampyaO, for each sample, the average corroded volume Vcmo _yCT is determined by J formula Vc .. _lW yen ⁼ [/ 4 (n H 22..)] - Vr _mci y _¾ - _î for each sample, the average corrosion rate Vu, expressed in μιη / η is determined by the formula:.

The average "Vu" corrosion rate of a sample gives an evaluation of the corrosion resistance of the test sample. Thus, the lower the corrosion rate of a sample, the higher its resistance to corrosion by molten glass,

The roughness index Ir of the sample i, Ir *, is determined by the following formula:

lr _; - [l OO.tVcmoywi reference sample) ^ Vcmoyeo reference sample - sample AV i)] - 100 _t da s wherein AV = <Vc _m0 ye_i ^■■■■ VCM)

The standardized test PRE IIL26 PRE R, 5, 1/78 was used to evaluate the thermal shock resistance by measuring the relative loss of bending strength (な OR loss) after one or more thermal cycles, each thermal cycle. It consists of heating the test specimen from room temperature to a temperature T of 800 ^to C, maintaining it at this temperature T for 30 minutes, then plunging it into cold water. The test pieces are bars 125 x 25 x 25 mm ³ having no skin face,

The resistance to bending was measured according to ISO 5014. For a given composition, the measurement of the initial flexural strength of the specimens (still not subject to heat shock), or "initial MOR," is the average value. measured on 3 identical test pieces. Measuring the resistance after shock mermique 800 ⁵ C. or "MOR after TB" is the average value of the flexural strength measured at room temperature on three test pieces after they have undergone said ennique shock. The measure of the relative loss of flexural strength, or "% Loss MOR", is given by the following formula:

% Loss MUR - 100. (MO after CT - initial MOR) ( ^' initial MOR)

The characteristics of the porticular mixtures tested and the test results are shown in Table 2 below: 23

24

24

Un indice de rugosité inférieur à 15 est représentatif d'une usure régulière et uniforme, Une comparaison des produits des exemples 1 * et 4 montre que pour des teneurs totales en oxyde de chrome similaires, le produit selon l'exemple 4 présente, après essai de corrosion, un indic de rugosité plus de trois fois inférieur à celui de l'exemple 1 * ainsi qu'une résistance à la corrosion remarquable. Une comparaison des produits des exemples 5* d' une part et 7 et 9 et 10 d'autre part conduit à une conclusion similaire,, l'exemple 7 comportant cependant de la iircone,

A roughness index of less than 15 is representative of uniform and uniform wear. A comparison of the products of Examples 1 * and 4 shows that for similar total chromium oxide contents, the product according to Example 4 shows, after test corrosion, a roughness indicative more than three times lower than that of Example 1 * and a remarkable corrosion resistance. A comparison of the products of Examples 5 * on the one hand and 7 and 9 and 10 on the other hand leads to a similar conclusion, Example 7 however comprising iircone,

 A comparison of the products of Examples 1 * on the one hand and 2 and 3 on the other hand shows that the products according to Examples 2 and 3 have a roughness index much lower than that of the product of Example 1 *. In addition, despite a lower chromium content, the products according to Examples 2 and 3 have a resistance to corrosion by molten glass similar to or greater than that of Example 1 *,

 The same observation can be made by comparing the products of Examples 6 and 5 *.

A comparison of the product of Example 5 * with the product of Example S shows that the latter, which comprises titanium oxide, has a much lower roughness index.

 Finally, a comparison of the products of Examples 9 and 10 shows that the product of Example 9, comprising 1% of granules, on the basis of the mass of the grains, has a higher thermal shock resistance than that of Example 10 which has substantially no granules, at a substantially equivalent mean corrosion rate and roughness index,

As is now clear, the invention provides a particulate mixture for making refractory products particularly well suited for contacting molten glass. In use, these products wear out remarkably uniformly, which leads to a considerable increase in their lifetime,

Of course, the invention is not limited to the examples provided for illustrative purposes.

Claims

1. Apparatus selected from a glassware furnace and a glass distribution channel comprising a block and / or a coating of a sintered product obtained by sintering a particulate mixture consisting of a matrix fraction and a granulate respectively constituted by particles having a size less than or equal to 50 μηι, called "matrix particles" and particles having a size greater than 50 μπι, called "grains", the matrix fraction representing more than 10% and less than 45% of the mass of the mixture particulate.  said particulate mixture having an AlO 3 content greater than 60%, in weight percent on the oxide basis, and having a chromium oxide content, denoted "Crr", of between 10% and 82%, preferably between 10 and 80%, as a percentage by weight based on the oxides of the refractory mixture,  the matrix fraction of said particulate mixture being such that  0.39 (Crr) -24 <Ct <0.39 (& τ) -52 (¹), Cr.M designating the mass content of chromium oxide of the matrix fraction, in percentage by mass on the basis of the oxides of the matrix, and the aggregate being such that x _n > 97%, _m ≥ 70%, and r v m m - 70%  - C な denoting the mass content of chromium oxide of a grain, in percentage by mass based on the oxides of this grain,  XJI denoting the quantity, in mass percentage on the basis of the granulate, of grains complying with the following condition (II): if 10% ≤ CTT <30%, then Cr _G 0.018 (Cp _r ) ² - 0.390 (Crr) -58.8; ^■ if 30% <Crr≤ 60%, then Cr ₀ <l, 22 (Cr _T ) - 26.7; (II) if 60% <CTT <82%, especially if Crr <80%, then Cr _G £ 100, - m denoting the quantity, in mass percentage on the basis of the granulate, of grains complying with the following condition (III):  - if 10% ≤ Crr≤ 30%, then 0.01 8. (ΟΓΤ) ^: -0.39Ο (ΟΓΤ),, 10 Cr Cr _G ≤ 0.01 8, (Cr _T ) ² -0.390 (CrT) -25.10; ^■ if 30% <Crr≤ 60%, then 1.17 (CrT) -21.5 <Cr _G <0.17 (Cr _T ) -5.5; (ΪΠ) ^■■ if 60% <Crr ≤ 82%, especially if Cr _T <80%, then 1.17 (Cr _R ) -21, 5 <Cr _G ≤1.67, (CT _T ) -35.5, xiv denoting the quantity, in mass percentage on the basis of the aggregate, of grains complying with the following condition (IV): - If 10% ≤ Cr _T 30%, then 0 _l 018. (Cr _T ) ² -0.390 (Crr) -9 ₁ 10> Cr _c ,; - If 30% <Crr <60%, then 1, 17, (Cr _T ) -21, 5> Cr _G ; (IV) - If 60% <Cr _T ≤ 82%, especially if Cr _T <80%, then 1, 17 (Crr) -21.5> Cr _G. 2, Device according to the preceding claim, the grains containing chromium oxide of said particulate mixture being Mttécs particles.  3, Device according to any one of the preceding claims, the granulate of said particulate mixture having a median circularity greater than 0.87, 4. Device according to the preceding claim, said particulate mixture being such that o≥ 99%.  5. Device according to any one of the preceding claims, said particulate mixture being such that  0.39 (Crr) -29 <<¾, <0.39 (Crr) -47 (V) 6. Device according to the preceding claim, said particulate mixture being such that 0.39 (Crr) -32 <Cr _M <0.39, (Ογ) - 4.5 (VI) 7. Device according to any one of the preceding claims, at least 70% by weight of the grains of said particulate mixture having, in percentage by mass on the basis of the oxides, a chromium oxide content satisfying the following condition (VII): - If 10% ≤ Cr _T ≤ 30%, then 0.018, (CrT) ² .0.390, (Cr:) - 13.10 Cr Cr _a <0.018 (Cr _T ) ² -0.390 (CrTh21.10; ■ If 30% <Crr≤ 60%, then 1,17 (Cr _T ) -17,5 <Cr _G <1,17. (Crr) -9, S; - If 60% <Crr <82%, especially if Cr _T ≤ 80%, then 1.67 (Crr) -51, 5 Cr Cr _G <l, 67 (Cr _r ) -39.5. 8. Device according to the preceding claim, said particulate mixture being such that, in said condition (VII), if 60% <Cr _T ≤ 82%, in particular if Crr≤ 80%, then 1.67. (Cr _T ) - 47.5 Cr Cr _G. 9, Device according to any one of the preceding claims, at least 90% by weight of the grains of said particulate mixture having a content of chromium oxide "Cr _G " complying with the condition (III) - If 10% ≤ Crr≤ 30%, then 0.018. (Cr _r ) ² -0 ₎ 390. (Cr _T h9 ₁ 10 Cr Cr _G ≤ O | - If 30% <Cr _r ≤ 60%, then 1.17 (Crr) -21.5≤Cr ₀ ≤ 1.17 (Crr) -5.5; - If 60% <Cr _T ≤ 82%, especially if Cr _r ≤ 80%, then 1. 17 (Cr _T ) -21, 5 <Cr _c <1, 67, (Crr) -35.5;  and where the condition (VIT)  ·· If 10% Gold <30%, then 0.01 8, (Cr _T ) ² -0 _> 30 (CrT) ÷ 13.10 Cr Cr _G ≤ 0.018, (Cr _T ) ² -0.390 (CrT>1.10; - If 30% <Cr _T <60%, then l, 17. (CPr) -17.5≤Cr _has ≤ 1.17 (Crr) -9.5; ^■■■ If 60% <CTJ ≤ 82%, especially if Cr _T ≤ 80%, then 1.67 (CT _t ) -51, 5 ≤ Cr _c <l, 67 (Cr) -39.5. 10. Apparatus according to any preceding claim, said particulate mixture being such that, regardless of ^'whether the component concerned, provided its content is greater than 1% by mass percentage based on oxides, standard deviation the distribution of its content between the different grains of said particulate mixture is less than 8. 11. Apparatus according to any preceding claim, said particulate mixture having a content of C ^ Oj ^■ - greater than 80% Al2O3, in weight percent on the oxide basis. 12. Device according to any one of the preceding claims, at least 70% by weight of the grains of said particulate mixture having, in percentages by weight on the basis of the oxides, a chromium oxide content complying with the following condition (VII): - If 10% <Cr _T ≤30%, then 0.018 (Cr _T ) ^; -0.390 (CrT> -l 3.10 <Cr _G ≤ 0.01 8, (Cr _T ) ² .0.390 (Cr _T ) -21 _! 10; - If 30% <Cn≤ 60%, then 1,17 (Cr _T ) -17,5 <Cr _G ≤ 1,17 (Crr) -9,5; - If 60% <Cr _T <82%, especially if Cr _T ≤ 80%, then 1.67 (Cr-r) -51, 5 Cr Cr _G <1.67 (Crr) -39.5. 13. Device according to the preceding claim, said particulate mixture having a content of Cr ^ Oj ^■ - ^■ ΛΙ2Ο3 greater than 90%, by percentage weight sr the oxide basis. 14. Device according to any one of the preceding claims, the matrix traction of said particulate mixture being composed of particles composed of chromium oxide and / or alumina and / or zirconia and / or magnesia and / or iron oxide and ^'or et'ou titanium oxide of silica and / or * calcium oxide, or consists of a mixture of such particles; and or the granular material formed by the grains of said particulate mixture being composed of particles of chromium oxide and / or alumina and / or zirconia and / or magnesia and / or iron oxide and / or oxide of titanium and ^/ or silica, or consists of a mixture of such particles. 15, Apparatus according to one of the preceding claims, at least 80% by weight of grains of said particulate mixture having a chemical composition such as. in percentages by weight on the basis of the oxides and for a total of 100%; - Cr ₂ 0 ₃ - ΛΙ2Ο3 + ZrC¾ - gO - Fea0 ₃ * If <な - T1O2> 90%, Cr ₂ 0 ₃ - AI3O.1 ^■ + ^■ MgO≥ 60%, and Cr ₂ 0 ₃ ≥ 9%, ci 20% ≥ Si0 ₂ 0.1%. and  other oxides: ≤ 10%. 16. The device as claimed in any one of the preceding claims, the matrix fraction of said particulate mixture consisting of chromium oxide particles of one pan and, on the other hand, particles of alumina and / or particles of nrcone. and / or particles of magnesia and / or iron oxide particles and / or titanium oxide particles and / or silica particles and ^; or particles of calcium oxide, or consisting of particles composed of chromium oxide on the one hand, and of alumina and / or of the circumfunction and / or magnesia and or oxide of iron and / or titanium oxide and / or silica and ^; or calcium, or mixtures of such particles. 17. The device as claimed in claim 1, wherein the granulate of said particulate mixture has a bulk density greater than 85% of the theoretical density and an open porosity of less than 3%. 8. The device as claimed in any one of the preceding claims, said particulate mixture being such that Crr≤80%.